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package javax.xml.transform;

/**
 * <p>A TransformerFactory instance can be used to create
 * {@link javax.xml.transform.Transformer} and
 * {@link javax.xml.transform.Templates} objects.</p>
 *
 * <p>The system property that determines which Factory implementation
 * to create is named <code>"javax.xml.transform.TransformerFactory"</code>.
 * This property names a concrete subclass of the
 * <code>TransformerFactory</code> abstract class. If the property is not
 * defined, a platform default is be used.</p>
 *
 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @author <a href="mailto:Neeraj.Bajaj@sun.com">Neeraj Bajaj</a>
 * @since 1.5
 */
public abstract class TransformerFactory {

  /**
   * Default constructor is protected on purpose.
   */
  protected TransformerFactory() {
  }


  /**
   * <p>Obtain a new instance of a <code>TransformerFactory</code>.
   * This static method creates a new factory instance.</p>
   * <p>This method uses the following ordered lookup procedure to determine
   * the <code>TransformerFactory</code> implementation class to
   * load:</p>
   * <ul>
   * <li>
   * Use the <code>javax.xml.transform.TransformerFactory</code> system
   * property.
   * </li>
   * <li>
   * Use the properties file "lib/jaxp.properties" in the JRE directory.
   * This configuration file is in standard <code>java.util.Properties
   * </code> format and contains the fully qualified name of the
   * implementation class with the key being the system property defined
   * above.
   * <br>
   * The jaxp.properties file is read only once by the JAXP implementation
   * and it's values are then cached for future use.  If the file does not exist
   * when the first attempt is made to read from it, no further attempts are
   * made to check for its existence.  It is not possible to change the value
   * of any property in jaxp.properties after it has been read for the first time.
   * </li>
   * <li>
   * Use the service-provider loading facilities, defined by the
   * {@link java.util.ServiceLoader} class, to attempt to locate and load an
   * implementation of the service using the {@linkplain
   * java.util.ServiceLoader#load(java.lang.Class) default loading mechanism}:
   * the service-provider loading facility will use the {@linkplain
   * java.lang.Thread#getContextClassLoader() current thread's context class loader}
   * to attempt to load the service. If the context class
   * loader is null, the {@linkplain
   * ClassLoader#getSystemClassLoader() system class loader} will be used.
   * </li>
   * <li>
   * Otherwise, the system-default implementation is returned.
   * </li>
   * </ul>
   *
   * <p>Once an application has obtained a reference to a <code>
   * TransformerFactory</code> it can use the factory to configure
   * and obtain transformer instances.</p>
   *
   * @return new TransformerFactory instance, never null.
   * @throws TransformerFactoryConfigurationError Thrown in case of {@linkplain
   * java.util.ServiceConfigurationError service configuration error} or if the implementation is
   * not available or cannot be instantiated.
   */
  public static TransformerFactory newInstance()
      throws TransformerFactoryConfigurationError {

    return FactoryFinder.find(
            /* The default property name according to the JAXP spec */
        TransformerFactory.class,
            /* The fallback implementation class name, XSLTC */
        "com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl");
  }

  /**
   * <p>Obtain a new instance of a <code>TransformerFactory</code> from factory class name.
   * This function is useful when there are multiple providers in the classpath.
   * It gives more control to the application as it can specify which provider
   * should be loaded.</p>
   *
   * <p>Once an application has obtained a reference to a <code>
   * TransformerFactory</code> it can use the factory to configure
   * and obtain transformer instances.</p>
   *
   * <h2>Tip for Trouble-shooting</h2>
   * <p>Setting the <code>jaxp.debug</code> system property will cause
   * this method to print a lot of debug messages
   * to <code>System.err</code> about what it is doing and where it is looking at.</p>
   *
   * <p> If you have problems try:</p>
   * <pre>
   * java -Djaxp.debug=1 YourProgram ....
   * </pre>
   *
   * @param factoryClassName fully qualified factory class name that provides implementation of
   * <code>javax.xml.transform.TransformerFactory</code>.
   * @param classLoader <code>ClassLoader</code> used to load the factory class. If
   * <code>null</code> current <code>Thread</code>'s context classLoader is used to load the factory
   * class.
   * @return new TransformerFactory instance, never null.
   * @throws TransformerFactoryConfigurationError if <code>factoryClassName</code> is
   * <code>null</code>, or the factory class cannot be loaded, instantiated.
   * @see #newInstance()
   * @since 1.6
   */
  public static TransformerFactory newInstance(String factoryClassName, ClassLoader classLoader)
      throws TransformerFactoryConfigurationError {

    //do not fallback if given classloader can't find the class, throw exception
    return FactoryFinder.newInstance(TransformerFactory.class,
        factoryClassName, classLoader, false, false);
  }

  /**
   * <p>Process the <code>Source</code> into a <code>Transformer</code>
   * <code>Object</code>.  The <code>Source</code> is an XSLT document that
   * conforms to <a href="http://www.w3.org/TR/xslt">
   * XSL Transformations (XSLT) Version 1.0</a>.  Care must
   * be taken not to use this <code>Transformer</code> in multiple
   * <code>Thread</code>s running concurrently.
   * Different <code>TransformerFactories</code> can be used concurrently by
   * different <code>Thread</code>s.</p>
   *
   * @param source <code>Source </code> of XSLT document used to create <code>Transformer</code>.
   * Examples of XML <code>Source</code>s include {@link javax.xml.transform.dom.DOMSource
   * DOMSource}, {@link javax.xml.transform.sax.SAXSource SAXSource}, and {@link
   * javax.xml.transform.stream.StreamSource StreamSource}.
   * @return A <code>Transformer</code> object that may be used to perform a transformation in a
   * single <code>Thread</code>, never <code>null</code>.
   * @throws TransformerConfigurationException Thrown if there are errors when parsing the
   * <code>Source</code> or it is not possible to create a <code>Transformer</code> instance.
   * @see <a href="http://www.w3.org/TR/xslt"> XSL Transformations (XSLT) Version 1.0</a>
   */
  public abstract Transformer newTransformer(Source source)
      throws TransformerConfigurationException;

  /**
   * <p>Create a new <code>Transformer</code> that performs a copy
   * of the <code>Source</code> to the <code>Result</code>.
   * i.e. the "<em>identity transform</em>".</p>
   *
   * @return A Transformer object that may be used to perform a transformation in a single thread,
   * never null.
   * @throws TransformerConfigurationException When it is not possible to create a
   * <code>Transformer</code> instance.
   */
  public abstract Transformer newTransformer()
      throws TransformerConfigurationException;

  /**
   * Process the Source into a Templates object, which is a
   * a compiled representation of the source. This Templates object
   * may then be used concurrently across multiple threads.  Creating
   * a Templates object allows the TransformerFactory to do detailed
   * performance optimization of transformation instructions, without
   * penalizing runtime transformation.
   *
   * @param source An object that holds a URL, input stream, etc.
   * @return A Templates object capable of being used for transformation purposes, never
   * <code>null</code>.
   * @throws TransformerConfigurationException When parsing to construct the Templates object
   * fails.
   */
  public abstract Templates newTemplates(Source source)
      throws TransformerConfigurationException;

  /**
   * <p>Get the stylesheet specification(s) associated with the
   * XML <code>Source</code> document via the
   * <a href="http://www.w3.org/TR/xml-stylesheet/">
   * xml-stylesheet processing instruction</a> that match the given criteria.
   * Note that it is possible to return several stylesheets, in which case
   * they are applied as if they were a list of imports or cascades in a
   * single stylesheet.</p>
   *
   * @param source The XML source document.
   * @param media The media attribute to be matched.  May be null, in which case the prefered
   * templates will be used (i.e. alternate = no).
   * @param title The value of the title attribute to match.  May be null.
   * @param charset The value of the charset attribute to match.  May be null.
   * @return A <code>Source</code> <code>Object</code> suitable for passing to the
   * <code>TransformerFactory</code>.
   * @throws TransformerConfigurationException An <code>Exception</code> is thrown if an error
   * occurings during parsing of the <code>source</code>.
   * @see <a href="http://www.w3.org/TR/xml-stylesheet/"> Associating Style Sheets with XML
   * documents Version 1.0</a>
   */
  public abstract Source getAssociatedStylesheet(
      Source source,
      String media,
      String title,
      String charset)
      throws TransformerConfigurationException;

  /**
   * Set an object that is used by default during the transformation
   * to resolve URIs used in document(), xsl:import, or xsl:include.
   *
   * @param resolver An object that implements the URIResolver interface, or null.
   */
  public abstract void setURIResolver(URIResolver resolver);

  /**
   * Get the object that is used by default during the transformation
   * to resolve URIs used in document(), xsl:import, or xsl:include.
   *
   * @return The URIResolver that was set with setURIResolver.
   */
  public abstract URIResolver getURIResolver();

  //======= CONFIGURATION METHODS =======

  /**
   * <p>Set a feature for this <code>TransformerFactory</code> and <code>Transformer</code>s or
   * <code>Template</code>s created by this factory.</p>
   *
   * <p> Feature names are fully qualified {@link java.net.URI}s. Implementations may define their
   * own features. An {@link TransformerConfigurationException} is thrown if this
   * <code>TransformerFactory</code> or the <code>Transformer</code>s or <code>Template</code>s it
   * creates cannot support the feature. It is possible for an <code>TransformerFactory</code> to
   * expose a feature value but be unable to change its state. </p>
   *
   * <p>All implementations are required to support the {@link javax.xml.XMLConstants#FEATURE_SECURE_PROCESSING}
   * feature. When the feature is:</p> <ul> <li> <code>true</code>: the implementation will limit
   * XML processing to conform to implementation limits and behave in a secure fashion as defined by
   * the implementation. Examples include resolving user defined style sheets and functions. If XML
   * processing is limited for security reasons, it will be reported via a call to the registered
   * {@link ErrorListener#fatalError(TransformerException exception)}. See {@link
   * #setErrorListener(ErrorListener listener)}. </li> <li> <code>false</code>: the implementation
   * will processing XML according to the XML specifications without regard to possible
   * implementation limits. </li> </ul>
   *
   * @param name Feature name.
   * @param value Is feature state <code>true</code> or <code>false</code>.
   * @throws TransformerConfigurationException if this <code>TransformerFactory</code> or the
   * <code>Transformer</code>s or <code>Template</code>s it creates cannot support this feature.
   * @throws NullPointerException If the <code>name</code> parameter is null.
   */
  public abstract void setFeature(String name, boolean value)
      throws TransformerConfigurationException;

  /**
   * Look up the value of a feature.
   *
   * <p> Feature names are fully qualified {@link java.net.URI}s. Implementations may define their
   * own features. <code>false</code> is returned if this <code>TransformerFactory</code> or the
   * <code>Transformer</code>s or <code>Template</code>s it creates cannot support the feature. It
   * is possible for an <code>TransformerFactory</code> to expose a feature value but be unable to
   * change its state. </p>
   *
   * @param name Feature name.
   * @return The current state of the feature, <code>true</code> or <code>false</code>.
   * @throws NullPointerException If the <code>name</code> parameter is null.
   */
  public abstract boolean getFeature(String name);

  /**
   * Allows the user to set specific attributes on the underlying
   * implementation.  An attribute in this context is defined to
   * be an option that the implementation provides.
   * An <code>IllegalArgumentException</code> is thrown if the underlying
   * implementation doesn't recognize the attribute.
   * <p>
   * All implementations that implement JAXP 1.5 or newer are required to
   * support the {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_DTD}  and
   * {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_STYLESHEET} properties.
   * </p>
   * <ul>
   * <li>
   * <p>
   * Access to external DTDs in the source file is restricted to the protocols
   * specified by the {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_DTD} property.
   * If access is denied during transformation due to the restriction of this property,
   * {@link javax.xml.transform.TransformerException} will be thrown by
   * {@link javax.xml.transform.Transformer#transform(Source, Result)}.
   * </p>
   * <p>
   * Access to external DTDs in the stylesheet is restricted to the protocols
   * specified by the {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_DTD} property.
   * If access is denied during the creation of a new transformer due to the
   * restriction of this property,
   * {@link javax.xml.transform.TransformerConfigurationException} will be thrown
   * by the {@link #newTransformer(Source)} method.
   * </p>
   * <p>
   * Access to external reference set by the stylesheet processing instruction,
   * Import and Include element is restricted to the protocols specified by the
   * {@link javax.xml.XMLConstants#ACCESS_EXTERNAL_STYLESHEET} property.
   * If access is denied during the creation of a new transformer due to the
   * restriction of this property,
   * {@link javax.xml.transform.TransformerConfigurationException} will be thrown
   * by the {@link #newTransformer(Source)} method.
   * </p>
   * <p>
   * Access to external document through XSLT document function is restricted
   * to the protocols specified by the property. If access is denied during
   * the transformation due to the restriction of this property,
   * {@link javax.xml.transform.TransformerException} will be thrown by the
   * {@link javax.xml.transform.Transformer#transform(Source, Result)} method.
   * </p>
   * </li>
   * </ul>
   *
   * @param name The name of the attribute.
   * @param value The value of the attribute.
   * @throws IllegalArgumentException When implementation does not recognize the attribute.
   */
  public abstract void setAttribute(String name, Object value);

  /**
   * Allows the user to retrieve specific attributes on the underlying
   * implementation.
   * An <code>IllegalArgumentException</code> is thrown if the underlying
   * implementation doesn't recognize the attribute.
   *
   * @param name The name of the attribute.
   * @return value The value of the attribute.
   * @throws IllegalArgumentException When implementation does not recognize the attribute.
   */
  public abstract Object getAttribute(String name);

  /**
   * Set the error event listener for the TransformerFactory, which
   * is used for the processing of transformation instructions,
   * and not for the transformation itself.
   * An <code>IllegalArgumentException</code> is thrown if the
   * <code>ErrorListener</code> listener is <code>null</code>.
   *
   * @param listener The new error listener.
   * @throws IllegalArgumentException When <code>listener</code> is <code>null</code>
   */
  public abstract void setErrorListener(ErrorListener listener);

  /**
   * Get the error event handler for the TransformerFactory.
   *
   * @return The current error handler, which should never be null.
   */
  public abstract ErrorListener getErrorListener();

}
